The invention is directed to improvements in fuel injection pumps for internal combustion engines.
This invention is an improvement upon a known fuel injection pump of this kind, embodied as a unit fuel injector and disclosed in German Offenlegungsschrift No. 35 23 536. In the known pump, the inflow line discharges with an inflow opening into the pump work chamber and is separated by the pump piston from the pump work chamber because of wear at the inflow opening. The instant the inflow opening opens is structurally defined and is determined by the distance of the inflow opening from bottom dead center of the pump piston.
The invention is a further improvement over a fuel injection pump of the radial piston type (German patent application No. P 36 12 942.9), in which the pump work chamber is defined by an annular groove on the rotating distributor piston; this annular groove communicates with fill grooves, which are distributed over the circumference of the distributor piston and are movable upon rotation of the distributor piston to communicate with fill bores in the distributor cylinder. The fill bores discharge into the fuel-filled pump interior and connect it to the pump work chamber whenever the fill grooves coincide with the mouths of the fill bores in the distributor cylinder.
In both of the above-described fuel injection pumps, the pump work chamber is always filled completely with fuel upon the intake stroke of the pump piston. The quantity of this fuel volume that attains injection is determined by the instant of closure and opening of the electric switching valve as a function of engine parameters, such as load and rpm. Upon closure of the switching valve, the fuel injection into the associated cylinder of the engine begins, while upon opening of the switching valve the pump work chamber is made to communicate with the relief chamber, thus abruptly terminating the fuel injection. If the switching valve malfunctions by sticking in the closed position and no longer opens, the fuel is always supplied with the maximum fuel injection quantity regardless of load, causing the engine rpm to increase uncontrollably, so that the engine "races".